Moq request: Allow overriding previously set mocked dbset

[bhood-zorus]

DbContextMock.CreateDbSetMock has the following line:

if (_dbSetCache.ContainsKey(entityType)) throw new ArgumentException($"DbSetMock for entity {entityType.Name} already created", nameof(dbSetSelector));

which effectively shuts off any attempt to override an existing set. There is no precedent for this in Moq; the following will execute without an exception and print "6".

void Main()
{
    var mock = new Mock<IFoo>();
    mock.Setup(x => x.Bar()).Returns(5);
    mock.Setup(x => x.Bar()).Returns(6);
    Console.WriteLine(mock.Object.Bar());
}

public interface IFoo
{
    int Bar();
}

My use case is I have a utility function that sets empty result sets for several different DbSets that's called in most test functions to create a default state, and then if the test specifically uses one DbSet then I override it there. I've created a workaround, but I also don't see a compelling reason to keep this behavior (or at least not make it configurable).